Metabolomics Analyses of 14 Classical Neurotransmitters by GC-TOF with LC-MS Illustrates Secretion of 9 Cell-Cell Signaling Molecules from Sympathoadrenal Chromaffin Cells in the Presence of Lithium.

The classical small molecule neurotransmitters are essential for cell-cell signaling in the nervous system for regulation of behaviors and physiological functions. Metabolomics approaches are ideal for quantitative analyses of neurotransmitter profiles but have not yet been achieved for the repertoire of 14 classical neurotransmitters. Therefore, this study developed targeted metabolomics analyses by full scan gas chromatography/time-of-flight mass spectrometry (GC-TOF) and hydrophilic interaction chromatography-QTRAP mass spectrometry (HILIC-MS/MS) operated in positive ionization mode for identification and quantitation of 14 neurotransmitters consisting of acetylcholine, adenosine, anandamide, aspartate, dopamine, epinephrine, GABA, glutamate, glycine, histamine, melatonin, norepinephrine, serine, and serotonin. GC-TOF represents a new metabolomics method for neurotransmitter analyses. Sensitive measurements of 11 neurotransmitters were achieved by GC-TOF, and three neurotransmitters were analyzed by LC-MS/MS (acetylcholine, anandamide, and melatonin). The limits of detection (LOD) and limits of quantitation (LOQ) were assessed for linearity for GC-TOF and LC-MS/MS protocols. In neurotransmitter-containing dense core secretory vesicles of adrenal medulla, known as chromaffin granules (CG), metabolomics measured the concentrations of 9 neurotransmitters consisting of the catecholamines dopamine, norepinephrine, and epinephrine, combined with glutamate, serotonin, adenosine, aspartate, glycine, and serine. The CG neurotransmitters were constitutively secreted from sympathoadrenal chromaffin cells in culture. Nicotine- and KCl-stimulated release of the catecholamines and adenosine. Lithium, a drug used for the treatment of bipolar disorder, decreased the constitutive secretion of dopamine and norepinephrine and decreased nicotine-stimulated secretion of epinephrine. Lithium had no effect on other secreted neurotransmitters. Overall, the newly developed GC-TOF with LC-MS/MS metabolomics methods for analyses of 14 neurotransmitters will benefit investigations of neurotransmitter regulation in biological systems and in human disease conditions related to drug treatments.

Neonatal catecholamine content of adrenal and extra-adrenal chromaffin tissue after prenatal exposure to dexamethasone.

We investigated the effects of prenatal exposure to dexamethasone on paraganglia and adrenal catecholamine stores in rabbit neonates. We compared pregnant rabbits injected with 0.01 mg x kg(-1) of dexamethasone (Dex) from day 24 to day 27 of gestation to an untreated group of unmanipulated rabbits. A group injected with 0.9% saline solution was added to evaluate the effect of injection and handling. Catecholamines were assessed by HPLC in offspring paraganglia and adrenal glands on days 0, 1, and 7 after birth. Data were analyzed by a two-factor ANOVA and Bonferroni-Dunn and t tests. Statistical significance was accepted at p < 0.05. Paraganglia catecholamine levels were significantly higher in the Dex animals than in the untreated ones at every maturational stage studied. For saline animals, the levels were lower than in the Dex group and higher than in the untreated one. In adrenal glands, the same pattern was observed for noradrenaline only. These findings suggest that such a treatment has a positive long-term effect on catecholamine levels of both structures with a more marked effect on paraganglia, an extra-adrenal structure exerting a main function during the perinatal period in providing the child with catecholamine stores.

Effects of 5-hydroxydopamine and 6-hydroxydopamine on the ultrastructure of type I cells in paraganglia of the rat recurrent laryngeal nerve.

The ultrastructure of the Type I cells in paraganglia of rat recurrent laryngeal nerve (RLN) was studied after the administration of 5-hydroxydopamine (5-OHDA) and 6-hydroxydopamine (6-OHDA). Normal Type I cells of RLN-paraganglia contained abundant organelles and their cytoplasm was characterized by the presence of numerous membrane-bounded dense-cored vesicles (DCVs). The DCVs were round in profile (diameter 107.67 +/- 0.06 nm, all values expressed as mean +/- s.e.m. in the present study) and possessed dense cores of moderate to low electron density. After 5-OHDA treatment (single injection, 100 mg/kg b.w., i.v.), the majority of DCVs were filled with a material of high electron density. No significant difference was observed between the profile diameter of the DCVs in 5-OHDA-treated rats (104.96 +/- 0.06 nm) and that in normal rats. After 6-OHDA treatment (three injections, 100 mg/kg b.w. each at 12 h intervals i.p.), no significant alteration in the electron density of the core was noted. However, most of the DCVs were enlarged and round, elliptical or irregular in profile (190.57 +/- 2.77 nm x 130.34 +/- 2.09 nm). The dense core of DCVs was centrally or eccentrically located in DCVs. The results of the present study indicate that: 1) there is only one type of granulated glomus cell (i.e., Type I cells) in the rat RLN-paraganglia under normal physiological condition; and 2) since the ultrastructural morphology of DCVs in Type I cells of rat RLN-paraganglia is altered after 5-OHDA or 6-OHDA treatment, these cells may possess mechanisms for the uptake of false adrenergic neurotransmitter and/or neurotoxin.

Ganglion cells and paraganglionic cells in the developing superior cervical ganglion of normal and p-chlorophenylalanine treated rats.

Ganglion cells and paraganglionic (PG) cells in the developing rat superior cervical ganglion were studied following postnatal treatment with p-chlorophenylalanine (pCPA) for 5 to 8 days. Litter mates, injected with saline solution, served as controls. Ganglion cells of control animals were differentiated ultrastructurally according to L. Eränkö (1972a) into late sympathicoblasts and young sympathetic nerve cells. In both maturation stages treatment with pCPA caused marked swelling of mitochondria, concomitant with minor changes of other cell organelles. Parallel to the ultrastructural alterations, fluorescence microscopy and cytophotometry revealed a slight diminution of diffuse fluorescence intensity in sympathetic neurons as the expression of a mainly extragranular amine depletion. In distinction from ganglion blocking agents the alterations are regarded as a general toxic effect of pCPA upon maturing sympathetic neurons, which secondarily influences catecholamine storage sites. Following treatment with pCPA, in PG-cells an alteration of mitochondria was scarcely to recognize. Specific granules were distinctly decreased in number, in some cases to an almost complete degree. Concordant to ultrastructural observations a marked diminution of fluorescence intensity was demonstrable in SIF-cells. In addition in these elements the fluorescence spectrum shifted towards the green field. Fluorescence cytophotometric evaluations confirmed the optical impression. Provided, that PG-cells, demonstrated with electron microscopy, are identical with SIF-cells in fluorescence microscopy, the results are discussed on the basis of a specific decrease of primary catecholamines due to an enzyme inhibition involved in catecholamine synthesis.

Effects of guanethidine on paraganglionic cells in the superior cervical ganglion of the rat.

Paraganglionic cells in the rat superior cervical ganglion were investigated by fluorescence and electron microscopy following treatment with guanethidine for 5-30 days. Control animals received saline and guanidine. Fluorescence cytophotometric measurements revealed a general decrease in the catecholamine content of paraganglionic cells in guanethidine-treated animals. However a few cell clusters showed focal increases. Similarly by electron microscopy there was a general decrease of cell clusters showing increases. -- guanethidine -- as well as guanidine--treated animals showed non-specific cytological alterations such as mitochondrial swelling and increase of cytoplasmic glycogen. However no changes of catecholamine contents and of dense core vesicles were noted in control animals. These results confirm the conception that in rat paraganglionic cells the dense core vesicles are the main storage site of catecholamines. The marked difference in the response of some cell culsters to the experimental treatment can be considered as evidence of functional heterogeneity of this cell population in the rat superior cervical ganglion.